JPWO2005096416A1 - Method for producing lithium-containing composite oxide for positive electrode of lithium secondary battery - Google Patents

Abstract

Provided is a positive electrode active material for a lithium secondary battery having a large volumetric capacity density, high safety, excellent uniform coatability, and excellent charge / discharge cycle durability and low temperature characteristics even at a high charge voltage. General formula LipNxMmOzFa (where N is at least one element selected from the group consisting of Co, Mn and Ni, and M is at least selected from the group consisting of transition metal elements other than N, Al and alkaline earth metal elements) One element: 0.9 ≦ p ≦ 1.2, 0.9 ≦ x <1.00, 0 <m ≦ 0.03, 1.9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02), which is a method for producing a lithium-containing composite oxide, a solution in which a complex containing M element (M element-containing complex) is dissolved in an organic solvent, an N source, a lithium source , And if necessary, using a fluorine source, through a mixing process, an organic solvent removal process and a baking process.

Description

  The present invention provides a method for producing a lithium-containing composite oxide for a positive electrode of a lithium secondary battery, which has a large volumetric capacity density, high safety, excellent charge / discharge cycle durability, and low-temperature characteristics, and a lithium-containing composite produced The present invention relates to a positive electrode for a lithium secondary battery including an oxide and a lithium secondary battery.

In recent years, as devices become more portable and cordless, demands for non-aqueous electrolyte secondary batteries such as lithium secondary batteries that are small, lightweight, and have high energy density are increasing. As such positive electrode active materials for non-aqueous electrolyte secondary batteries, composite oxides of lithium and transition metals such as LiCoO ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiMn ₂ O ₄ , LiMnO ₂ are known. Yes.

Among them, a lithium secondary battery using lithium-containing composite oxide (LiCoO ₂ ) as a positive electrode active material and using carbon such as lithium alloy, graphite, or carbon fiber as a negative electrode can obtain a high voltage of 4V, It is widely used as a battery having a high energy density.

However, in the case of a non-aqueous secondary battery using LiCoO ₂ as a positive electrode active material, further improvement in capacity density per unit volume and safety of the positive electrode layer is desired, and by repeatedly performing a charge / discharge cycle, There have been problems such as deterioration in cycle characteristics in which the battery discharge capacity gradually decreases, problems in weight capacity density, and large reductions in discharge capacity at low temperatures.

In order to solve a part of these problems, Patent Document 1 discloses that the average particle diameter of LiCoO ₂ that is a positive electrode active material is 3 to 9 μm, and the volume occupied by a particle group having a particle diameter of 3 to 15 μm is the total volume. By setting the diffraction peak intensity ratio between 2θ = about 19 ° and 2θ = 45 ° measured by X-ray diffraction using CuKα as a radiation source to a specific value, the coating characteristics, self-discharge characteristics, It has been proposed to make an active material excellent in cycle performance. Further, the publication proposes a preferred embodiment in which the particle size of LiCoO ₂ does not substantially have a particle size distribution of 1 μm or less or 25 μm or more. However, such a positive electrode active material has improved coating characteristics and cycle characteristics, but has not been sufficiently satisfactory in safety, volume capacity density, and weight capacity density.

Moreover, in order to solve the problem regarding battery characteristics, Patent Document 2 proposes to replace 5 to 35% of Co atoms with W, Mn, Ta, Ti, or Nb in order to improve cycle characteristics. In Patent Document 3, hexagonal LiCoO ₂ having a c-axis length of a lattice constant of not more than 14.051 mm and a crystallite diameter in the (110) direction of 45 to 100 nm is used as a positive electrode active material. It has been proposed to improve cycle characteristics.

Further, Patent Document 4 has the formula Li _x Ni _1-m N _m O ₂ (where 0 <x <1.1, 0 ≦ m ≦ 1), and the primary particles are plate-like or Lithium composite oxide having a columnar shape and (volume-based cumulative 95% diameter−volume-based cumulative 5% diameter) / volume-based cumulative 5% diameter of 3 or less and an average particle diameter of 1 to 50 μm is It has been proposed that the initial discharge capacity is high and the charge / discharge cycle durability is excellent.

  In Patent Document 5, primary particles having an average particle diameter of 0.01 to 2 μm and agglomeration of primary particles of cobalt hydroxide, cobalt oxyhydroxide, and cobalt oxide are aggregated. It has been proposed to lithiate cobalt compound powders that have formed secondary particles. However, even in this case, a positive electrode material having a high volume capacity density cannot be obtained, and the cycle characteristics, safety and large current discharge characteristics are still insufficient.

As described above, in the above-described conventional technology, in a lithium secondary battery using a lithium composite oxide as a positive electrode active material, all of volume capacity density, safety, coating uniformity, cycle characteristics, and low temperature characteristics are all achieved. We have not yet obtained a satisfactory content.
JP-A-6-2443897 Japanese Patent Laid-Open No. 3-201368 JP 10-31805 A JP-A-10-72219 JP 2002-60225 A

  The present invention is a method for producing a lithium-containing composite oxide for a lithium secondary battery positive electrode, which has a large volumetric capacity density, high safety, excellent charge / discharge cycle durability, and excellent low-temperature characteristics, It aims at provision of the positive electrode for lithium secondary batteries containing a lithium containing complex oxide, and a lithium secondary battery.

  As a result of intensive research, the present inventor has reached the present invention through the following findings. That is, lithium-containing composite oxides such as lithium cobaltate basically have excellent volume capacity density, but the crystal structure of hexagonal crystals and monoclinic crystals as lithium enters and exits during charging and discharging. Since the phase transition occurs and the expansion and contraction are repeated, there is a problem that the crystal structure is broken and the cycle characteristics are deteriorated. As described above, this problem is solved by substituting a part of cobalt of lithium cobaltate with a specific additive element such as W, Mn, Ta, Ti, or Nb and stabilizing the crystal structure. Yes.

  However, in the case of the above-described conventional method, the intended result is not necessarily obtained. That is, with conventional mixing of powders by solid phase, it is difficult to mix the powders uniformly, and the obtained composite oxide does not have a uniform composition throughout and is also regarded as partly an impurity phase. Will have a non-uniform composition. In order to solve this, a coprecipitation method for uniformly depositing all the components forming the composite oxide from the liquid phase has been studied, but there is a problem that it is difficult to control the composition and particle size.

The inventor has a general formula Li _p N _x M _m O _{z Fa} (where N is at least one element selected from the group consisting of Co, Mn and Ni, and M is a transition metal element other than N, It is at least one element selected from the group consisting of Al and alkaline earth metal elements: 0.9 ≦ p ≦ 1.2, 0.9 ≦ x <1.00, 0 <m ≦ 0.03, 1 .9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02), the complex containing M element is an organic solvent as the M element source. A solution obtained by using a solution dissolved therein and mixing it with a compound powder containing other components, N element source, lithium source, and, if necessary, fluorine source alone or in combination, respectively. The above problems can be achieved by removing the organic solvent from It was found that it can be achieved.

Thus, the gist of the present invention is as follows.
(1) In formula _{Li p N x M m O z} F a ( where, N is at least one element selected from the group consisting of Co, Mn and Ni, M is a transition metal element other than N, Al and It is at least one element selected from the group consisting of alkaline earth metal elements: 0.9 ≦ p ≦ 1.2, 0.9 ≦ x <1.00, 0 <m ≦ 0.03, 1.9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02), wherein the complex containing M element is an organic solvent as the M element source. The manufacturing method of the lithium containing complex oxide for lithium secondary battery positive electrodes characterized by using the solution melt | dissolved in the.
(2) The M element complex is an M element chelate complex, an M element nitrate or chloride glycol complex, or an M element nitrate or chloride β-diketone complex, and the organic solvent is a polar organic solvent. The manufacturing method as described in said (1).
(3) The complex containing M element is a chelate complex of M element, a complex containing β-diketone group and alkoxide group of M element, and / or a complex of diethylene glycol and triethylene glycol of nitrate of M element ( The manufacturing method as described in 1).
(4) In any one of the above (1) to (3), the M element is at least one selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Mg, Cu, Sn, Zn, and Al. The manufacturing method as described.
(5) The above (1) to (4), wherein the M element comprises at least Al and Mg, Al / Mg is 1/5 to 5/1 in atomic ratio, and 0.002 ≦ m ≦ 0.025. The manufacturing method in any one of.
(6) M element consists of Mg and M2 (M2 is at least one element selected from the group consisting of at least Ti, Zr, Ta, and Nb), and M2 / Mg is in an atomic ratio of 1/40 to 2/1. And the production method according to any one of the above (1) to (4), wherein 0.002 ≦ m ≦ 0.025.
(7) A solution in which a complex containing M element is dissolved in an organic solvent, an N source compound powder, and, if necessary, a fluorine source compound powder are mixed, and after removing the organic solvent from the resulting mixture, a lithium source The production method according to any one of (1) to (6) above, wherein the compound powder and, if necessary, a fluorine source compound are added and mixed, and then fired at 800 to 1050 ° C. in an oxygen-containing atmosphere.
(8) A solution in which a complex containing M element is dissolved in an organic solvent, an N source compound powder, a lithium source compound powder, and, if necessary, a fluorine source compound powder are mixed, and the organic solvent is removed from the resulting mixture. Then, the manufacturing method according to any one of (1) to (6) above, wherein firing is performed at 800 to 1050 ° C. in an oxygen-containing atmosphere.
(9) Lithium source compound powder, N source compound powder, and, if necessary, fluorine source compound powder are mixed and fired to obtain a lithium-containing composite oxide powder and a complex containing M element dissolved in an organic solvent. The manufacturing method according to any one of (1) to (6) above, wherein the organic solvent is removed from the resulting mixture after mixing with the solution, and then fired at 300 to 1050 ° C. in an oxygen-containing atmosphere.
(10) The integral width of the diffraction peak of the (110) plane of 2θ = 66 to 67 ° measured by X-ray diffraction using CuKα as the radiation source of the lithium-containing composite oxide is 0.08 to 0.14, The manufacturing method according to any one of (1) to (9), wherein the surface area is 0.2 to 0.6 m ² / g and the heat generation start temperature is 160 ° C. or higher.
(11) The production method according to any one of (1) to (10), wherein the lithium-containing composite oxide has a filling press density of 3.15 to 3.60 g / cm ³ .
(12) The production method according to any one of (1) to (11), wherein the remaining alkali amount contained in the lithium-containing composite oxide is 0.03% by mass or less.
(13) A positive electrode for a lithium secondary battery comprising a lithium-containing composite oxide produced by the production method according to any one of (1) to (12).
(14) A lithium secondary battery using the positive electrode described in (13) above.

According to the present invention, a lithium-containing composite oxide having excellent characteristics for a lithium secondary battery positive electrode such as a large volumetric capacity density, high safety, excellent charge / discharge cycle durability, and excellent low temperature characteristics is obtained. And a method for producing a lithium-containing composite oxide having high productivity that is excellent in storage stability of the intermediate, and further, a positive electrode for a lithium secondary battery including the produced lithium-containing composite oxide, and A lithium secondary battery is provided.
The reason why such an excellent effect is achieved by the present invention is not necessarily clear, but is estimated as follows. That is, with the addition of M element in the conventional solid phase method, since the amount of M element added is very small, uniform addition to the N element material or the positive electrode material is difficult, and the desired effect of adding the M element is achieved. It was difficult to get. However, according to the method of the present invention, since it acts on the N element raw material or the positive electrode material in the form of a solution of M element, the M element can be uniformly dispersed in the pores of the positive electrode active material. Therefore, it is assumed that the effect of improving battery performance is exhibited. Further, since the M element is allowed to act on the N element compound or the positive electrode material, the composition of the positive electrode active material and the control of the particle size are easier than in the conventional coprecipitation method, and there is an industrial advantage.

Lithium-containing composite oxide for a lithium secondary battery positive electrode produced in the present invention is represented by the general formula _{Li p N x M m O z} F a. In this general formula, p, x, m, z and a are defined above. Among these, p, x, m, z and a are preferably as follows. 0.9 ≦ p ≦ 1.1, particularly preferably 0.97 ≦ p ≦ 1.03, 0.975 ≦ x <1.00, 0.002 ≦ m ≦ 0.025, 1.9 ≦ z ≦ 2.1, particularly preferably 1.95 ≦ z ≦ 2.05, x + m = 1, 0.001 ≦ a ≦ 0.01. Here, when a is larger than 0, a composite oxide in which some of the oxygen atoms are substituted with fluorine atoms is obtained. In this case, the safety of the obtained positive electrode active material is improved. In the present invention, the total number of cations atoms is equal to the total number of anions atoms. That is, it is preferable that the sum of p, x, and m is equal to the sum of z and a.

  N is at least one element selected from the group consisting of Co, Mn and Ni, and among them, Co, Ni, Co and Ni, Mn and Ni, and Co, Ni and Mn are preferable. M is at least one element selected from the group consisting of transition metal elements excluding N, Al, and alkaline earth metals. In the present invention, such an M element is sometimes referred to as an additive element. The transition metal element represents a transition metal of Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11 of the periodic table. Among these, M is preferably at least one element selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Mg, Cu, Sn, Zn, and Al. Among these, Ti, Zr, Hf, Mg, or Al is preferable from the viewpoint of capacity development, safety, cycle durability, and the like.

  In the present invention, in particular, M is composed of Al and Mg, and Al and Mg are preferably in an atomic ratio of 1/5 to 5/1, more preferably 1/3 to 3/1, and particularly preferably 2/3. ˜3 / 2, and preferably 0.002 ≦ m ≦ 0.025, more preferably 0.005 ≦ m ≦ 0.025, and particularly preferably 0.01 ≦ m ≦ 0.02. In some cases, the balance of battery performance, that is, the balance of initial weight capacity density, safety, and charge / discharge cycle stability is particularly favorable. In the present invention, M is composed of Mg and M2 (M2 is at least one element selected from the group consisting of Ti, Zr, Ta, and Nb), and M2 and Mg are preferably in atomic ratio. 1/40 to 2/1, particularly preferably 1/30 to 1/5, and preferably 0.002 ≦ m ≦ 0.025, more preferably 0.005 ≦ m ≦ 0.025, It is particularly preferable that 0.01 ≦ m ≦ 0.02 because the balance of battery performance, that is, the balance of initial weight capacity density, safety, and charge / discharge cycle stability is good.

  In the present invention, when the F element is contained, it is preferable that the F element is present on the surface of the lithium-containing composite oxide particles. The presence of these elements on the surface can improve important battery characteristics such as safety and charge / discharge cycle characteristics without causing a decrease in battery performance when added in a small amount. Whether or not these elements are present on the surface can be determined by performing spectroscopic analysis, for example, XPS analysis, on the positive electrode particles.

  In the method for producing a lithium-containing composite oxide of the present invention, the element M as an additive element is used in the form of a solution in which a complex containing the element M is dissolved in an organic solvent. This term refers to a solution in which a complex compound of M element is dissolved in an organic solvent or a complex is not formed before dissolving in the organic solvent, but the organic solvent and M element are dissolved to form a complex. It means the solution that is. Preferred examples of the complex element of M element in the former case include an M element chelate complex, a glycol complex of M element nitrate or M element chloride, or a β-diketone complex of M element nitrate or M element chloride. Is mentioned. As a chelating agent that forms an M element chelate complex, β-diketone compounds and glycol compounds are preferred. When the chelating agent is a β-diketone, a metal compound having both an alkoxide group and a β-diketone group is more preferable because it has high solubility in a solvent. As the glycol complex of M element nitrate or M element chloride, two or more kinds of glycols, preferably a mixture of diethylene glycol and triethylene glycol are preferable.

  The organic solvent used for preparing the solution in which the complex containing the M element is dissolved in the organic solvent is preferably a polar organic solvent. The polar organic solvent preferably has a boiling point of 60 to 200 ° C, particularly preferably 80 to 150 ° C. Preferred examples thereof include alcohols such as ethanol and 2-propanol, glycols such as hexylene glycol, and aromatic hydrocarbons such as xylene. In the polar organic solvent, a nonpolar solvent such as hexane may usually be contained in an amount of 30% by weight or less. The concentration of the complex containing the element M in the organic solvent is preferably larger in order to remove the organic solvent used in the subsequent step, for example, preferably 3 to 15% by weight, particularly preferably 5 to 10% by weight in terms of metal. % Is used.

In the present invention, the solution in which the complex containing the M element is dissolved in the organic solvent is then preferably mixed in the following mode (1), (2) or (3).
(1) An N source compound powder and, if necessary, a fluorine source compound powder and a solution in which a complex containing an M element is dissolved in an organic solvent are mixed.
(2) The N source compound powder, the lithium source compound powder and, if necessary, the fluorine source compound powder, and a solution in which a complex containing M element is dissolved in an organic solvent are mixed.
(3) An N source compound powder, a lithium source compound powder and, if necessary, a fluorine source compound powder are mixed and preferably 5 to 20 at 800 to 1050 ° C. (particularly preferably 900 to 1000 ° C.) in an oxygen-containing atmosphere. After the time firing, the lithium-containing composite oxide powder obtained by pulverization and classification is mixed with a solution in which a complex containing M element is dissolved in an organic solvent.

The mixing ratio of each component in the above, chosen so that the ratio of each element desired and within the scope of a general formula of the finally obtained positive-electrode active material described above _{Li p N x M m O z} F a . Further, the particle size of the N source compound powder and the fluorine source compound powder used as necessary is not particularly limited, but preferably 0.1 to 20 μm in order to achieve good mixing, Particularly preferably, 0.5 to 15 μm is selected.
As N source compound used here, when N is cobalt, cobalt carbonate, cobalt hydroxide, cobalt oxyhydroxide, and cobalt oxide are preferably used. In particular, cobalt hydroxide or cobalt oxyhydroxide is preferable because performance is easily exhibited. When N is nickel, nickel hydroxide and nickel carbonate are preferably used. When N is manganese, manganese carbonate is preferably used.

When the N element is a compound composed of two or more elements, it is preferable that the two or more elements are uniformly dispersed at the atomic level by coprecipitation. As a coprecipitation compound, a coprecipitation hydroxide, a coprecipitation oxyhydroxide, a coprecipitation oxide, a coprecipitation carbonate, etc. are preferable compounds. When N element consists of a compound of nickel and cobalt, the atomic ratio of nickel and cobalt is preferably 90:10 to 70:30. The cobalt may be partially substituted with aluminum or manganese. When N element consists of a compound of nickel, cobalt, and manganese, the atomic ratio of nickel, cobalt, and manganese is preferably (10-50) :( 7-40) :( 20-70), respectively.
Further, when N is a compound of nickel and cobalt, Ni _0.8 Co _0.2 OOH and Ni _0.8 Co _0.2 (OH) ₂ , but when N is a compound of nickel and manganese, Ni _{0 .5} Mn _0.5 OOH, when N is a compound of nickel, cobalt and manganese, Ni _0.4 Co _0.2 Mn _0.4 (OH) ₂ , Ni _1/3 Co _1/3 Mn _1/3 OOH is each preferably exemplified.

  As a method of obtaining the mixture with the solution of the complex containing M element according to the aspect of (1) above, an appropriate mixing means can be selected. For example, (A) N element in the solution of the complex containing M element A method of dispersing and stirring the source compound powder and, if necessary, the fluorine source compound powder, (B) spraying the N source compound powder, and optionally mixing the fluorine source compound powder, The method of spraying the solution of the complex containing can be illustrated.

  Moreover, it is preferable to mix with the solution of the complex containing M element by the aspect of said (1)-(3) sufficiently uniformly using an axial mixer etc. As the solid content concentration in the mixture, a higher concentration is preferable as long as it is uniformly mixed. Usually, the solid / liquid ratio is preferably 50/50 to 90/10, particularly preferably 60/40 to 80/20. It is.

  The organic solvent in the mixture is then removed from the mixture obtained by a suitable mixing means. The removal of the organic solvent is preferably performed by drying at 50 to 200 ° C., particularly preferably at 80 to 120 ° C., usually for 1 to 10 hours. Since the organic solvent in the mixture is incinerated in the subsequent baking step, it is not always necessary to completely remove it at this stage. However, since there is a concern about reduction of the raw material or the positive electrode material, it is removed as much as possible. Is preferred.

The mixture that has been mixed according to the above aspect (2) or (3) and from which the organic solvent has been removed as described above is fired by the method described below. On the other hand, the mixture that has been mixed according to the embodiment (1) and from which the organic solvent has been removed as described above is preferably pulverized into a powder of an appropriate size and mixed with the lithium source compound powder, and the mixture will be described later. Baking by means. Even in such mixing, it is preferable to use a stirrer such as an axial mixer or a drum mixer and mix sufficiently uniformly.
As the lithium source compound to be used, lithium carbonate or lithium hydroxide is preferably used in any of the above aspects (1), (2) or (3). In particular, lithium carbonate is preferable because it is inexpensive. Similarly, metal fluoride, LiF, MgF ₂ or the like is selected as the fluorine source. The particle size of the lithium source compound powder is not particularly limited, but is preferably 0.1 to 20 μm, particularly preferably 0.5 to 15 μm, in order to achieve good mixing.

Firing of the mixture obtained in the above aspect (1) or (2) is preferably performed at 800 to 1050 ° C. for 5 to 20 hours in an oxygen-containing atmosphere. When the firing temperature is less than 800 ° C., lithiation becomes incomplete, and when it exceeds 1050 ° C., charge / discharge cycle durability and initial capacity are lowered. In particular, the firing temperature is preferably 900 to 1000 ° C. The obtained fired product is cooled, pulverized and classified to produce lithium-containing composite oxide particles.
In the above aspect (3), an N source compound powder, a lithium reduced powder and, if necessary, a mixture containing a fluorine source compound powder can be obtained in the same manner as the mixing method described above. This mixture is fired in the same manner as described above. The mixture obtained in the above aspect (3), that is, the mixture of the lithium-containing composite oxide powder containing the M element-containing complex is fired at 300 to 1050 ° C. in an oxygen-containing atmosphere. When the firing temperature is lower than 300 ° C., the decomposition of the organic matter is insufficient, which is not preferable. Moreover, when it exceeds 1050 degreeC, charging / discharging circle durability and initial stage capacity | capacitance will fall. In particular, the firing temperature is preferably 400 to 900 ° C. The obtained fired product is cooled, pulverized and classified to produce lithium-containing composite oxide particles.

The lithium-containing composite oxide of the present invention thus produced has an average particle diameter D50 of preferably 8 to 18 μm, particularly preferably 10 to 16 μm, and a specific surface area of preferably 0.2 to 0.6 m ² / g, particularly preferably 0.3 to 0.5 m ² / g, (110) plane diffraction peak half-value width of 2θ = 66.5 ± 1 ° measured by X-ray diffraction using CuKα as a radiation source is preferably 0 0.08 to 0.14 °, particularly preferably 0.08 to 0.12 °, and the press density is preferably 3.15 to 3.60 g / cm ³ , particularly preferably 3.20 to 3.50 g / cm ^3. Is preferred. In addition, the press density in this invention means the apparent press density when press-compressing particle powder by the pressure of 0.3 t / cm < ² > unless there is particular notice including the description in an Example. In the lithium-containing composite oxide of the present invention, the amount of residual alkali contained therein is preferably 0.03% by mass or less, and particularly preferably 0.01% by mass or less.

  When producing a positive electrode for a lithium secondary battery from the lithium-containing composite oxide thus produced, a carbon-based conductive material such as acetylene black, graphite, and Ketchen black is added to the composite oxide powder. It is formed by mixing binders. For the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. The lithium-containing composite oxide powder, conductive material and binder of the present invention are made into a slurry or kneaded product using a solvent or a dispersion medium. This is supported on a positive electrode current collector such as an aluminum foil or a stainless steel foil by coating or the like to produce a positive electrode for a lithium secondary battery.

  In the lithium secondary battery using the lithium-containing composite oxide of the present invention as the positive electrode active material, a porous polyethylene film, a porous polypropylene film, or the like is used as the separator. Various solvents can be used as the solvent for the electrolyte solution of the battery, and among them, carbonate ester is preferable. The carbonate ester can be either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate (EC). Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate, methyl isopropyl carbonate, and the like.

  In this invention, the said carbonate ester can be used individually or in mixture of 2 or more types. Moreover, you may mix and use with another solvent. Moreover, depending on the material of the negative electrode active material, when a chain carbonate ester and a cyclic carbonate ester are used in combination, discharge characteristics, cycle durability, and charge / discharge efficiency may be improved.

In the lithium secondary battery using the lithium-containing composite oxide of the present invention as the positive electrode active material, a vinylidene fluoride-hexafluoropropylene copolymer (for example, product name: Kyner manufactured by Atchem Co.) or vinylidene fluoride-perfluoro is used. A gel polymer electrolyte containing a propyl vinyl ether copolymer may be used. Solutes added to the electrolyte solvent or polymer electrolyte include ClO ₄ —, CF ₃ SO ₃ —, BF ₄ —, PF ₆ —, AsF ₆ —, SbF ₆ —, CF ₃ CO ₂ —, (CF ₃ Any one or more of lithium salts having SO ₂ ) ₂ N— or the like as an anion is preferably used. It is preferable to add at a concentration of 0.2 to 2.0 mol / l (liter) with respect to the electrolyte solvent or polymer electrolyte made of the lithium salt. If it deviates from this range, the ionic conductivity is lowered and the electrical conductivity of the electrolyte is lowered. Of these, 0.5 to 1.5 mol / l is particularly preferable.

  In the lithium battery using the lithium-containing composite oxide of the present invention as the positive electrode active material, a material capable of inserting and extracting lithium ions is used as the negative electrode active material. The material for forming the negative electrode active material is not particularly limited. For example, an oxide, a carbon compound, a silicon carbide compound, or a silicon oxide compound mainly composed of lithium metal, lithium alloy, carbon material, periodic table 14 or group 15 metal. , Titanium sulfide, boron carbide compounds and the like. As the carbon material, those obtained by pyrolyzing an organic substance under various pyrolysis conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, flake graphite, and the like can be used. As the oxide, a compound mainly composed of tin oxide can be used. As the negative electrode current collector, a copper foil, a nickel foil, or the like is used. Such a negative electrode is preferably produced by kneading the active material with an organic solvent to form a slurry, and applying the slurry to a metal foil current collector, drying, and pressing.

There is no restriction | limiting in particular in the shape of the lithium battery which uses the lithium containing complex oxide of this invention for a positive electrode active material. A sheet shape, a film shape, a folded shape, a wound-type bottomed cylindrical shape, a button shape, or the like is selected depending on the application.
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1-1]
According to a known method, a cobalt hydroxide aqueous solution and ammonium hydroxide mixed solution and a caustic soda aqueous solution were continuously mixed to continuously prepare a cobalt hydroxide slurry. Next, the slurry was subjected to agglomeration, filtration, and drying steps to obtain cobalt hydroxide powder. The obtained cobalt hydroxide has a diffraction peak half-width of (001) plane of 2θ = 19 ± 1 ° in powder X-ray diffraction using CuKα ray is 0.27 °, and 2θ = 38 ° ± 1. The diffraction peak half-value width of the (101) plane was 0.23 °, and as a result of observation with a scanning electron microscope, it was found that the fine particles were aggregated and formed from substantially spherical secondary particles. As a result of volume-based particle size distribution analysis obtained from image analysis under scanning electron microscope observation, the average particle size D50 was 17.5 μm, D10 was 7.1 μm, and D90 was 26.4 μm. The cobalt content of the cobalt hydroxide powder was 61.5% by mass.

  On the other hand, 1.75 g of diethylene glycol and 2.47 g of triethylene glycol were added to 5.28 g of magnesium nitrate hexahydrate, and the mixture was stirred until completely dissolved. After complete dissolution, 33.82 g of ethanol was added and further stirred. To the obtained solution, 1.01 g of a mixed solution of titanium acetylacetonate in xylene / 1-butanol (1: 1) (Ti content: 9.8% by mass) was added, and aluminum ethyl acetoacetate diisopropylate was added in 5. 67 g was added and stirred to obtain a complex solution containing the additive element.

The cobalt hydroxide powder 193.18 g and the additive element solution were mixed in a slurry state. The slurry was desolvated with a rotary evaporator, mixed with 76.56 g of lithium carbonate powder having a specific surface area of 1.2 m ² / g, and stored at room temperature for 10 days. There was no particular change in the appearance after storage. This mixture was calcined in air at 950 ° C. for 12 hours. The composition of the obtained composite oxide was LiAl _0.01 Co _0.979 Mg _0.01
Ti _0.001 O ₂ .

The particle size distribution of the substantially spherical lithium-containing composite oxide powder formed by aggregation of the obtained primary particles was measured in an aqueous solvent using a laser scattering particle size distribution measuring device. As a result, the average particle diameter D50 was 15.9 μm, D10 was 6.5 μm, D90 was 23.5 μm, and the specific surface area determined by the BET method was 0.35 m ² / g. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.107 °. The press density of this powder was 3.24 g / cm ³ . 10 g of this lithium-containing composite oxide powder was dispersed in 100 g of pure water, filtered, and potentiometrically titrated with 0.1 N HCl to determine the residual alkali amount, which was 0.02% by mass.

  The lithium-containing composite oxide powder, acetylene black, and polyvinylidene fluoride powder are mixed at a mass ratio of 90/5/5, N-methylpyrrolidone is added to prepare a slurry, and aluminum having a thickness of 20 μm is prepared. The foil was coated on one side using a doctor blade. The positive electrode sheet for lithium batteries was produced by drying and performing roll press rolling 5 times.

The positive electrode sheet is used for the positive electrode, a metal lithium foil having a thickness of 500 μm is used for the negative electrode, a nickel foil of 20 μm is used for the negative electrode current collector, and a porous polypropylene having a thickness of 25 μm is used for the separator. Further, the electrolytic solution is a LiPF ₆ / EC + DEC (1: 1) solution having a concentration of 1 M (meaning a mixed solution of EC and DEC in a mass ratio (1: 1) containing LiPF ₆ as a solute. Solvents described later are also this). The two stainless steel simple sealed cell type lithium batteries were assembled in an argon glove box.

  For the one battery, the initial discharge capacity was charged at 25 ° C. with a load current of 75 mA per gram of the positive electrode active material to 4.3 V and discharged with a load current of 75 mA per gram of the positive electrode active material to 2.5 V. Asked. Furthermore, the density of the electrode layer was determined. Moreover, about this battery, the charging / discharging cycle test was done 30 times continuously. As a result, the initial weight capacity density of the positive electrode layer at 25 ° C. and 2.5 to 4.3 V was 162 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.3%.

  The other battery was charged at 4.3 V for 10 hours, disassembled in an argon glove box, and the charged positive electrode sheet was taken out. The positive electrode sheet was washed, punched out to a diameter of 3 mm, sealed in an aluminum capsule together with EC, and heated at a rate of 5 ° C./min with a scanning differential calorimeter to measure the heat generation start temperature. As a result, the heat generation start temperature of the 4.3V charged product was 174 ° C.

[Example 1-2]
To 5.28 g of magnesium nitrate hexahydrate, 1.75 g of diethylene glycol and 2.47 g of triethylene glycol were added and stirred until completely dissolved. After completely dissolved, 25.60 g of ethanol was added and stirred. To this solution, 9.24 g of a mixed solution of zirconium tributoxide monoacetylacetonate in xylene / 1-butanol (1: 1) (ZrO ₂ : 13.8% by mass) was added, and aluminum ethyl acetoacetate diisopropylate was added in an amount of 5.24 g. An additive element solution was prepared by adding 66 g and stirring.

A drying treatment was performed in the same manner as in Example 1-1 except that the complex solution containing the obtained additive element and 191.99 g of cobalt hydroxide powder were mixed. The obtained mixture and 76.40 g of lithium carbonate powder having a specific surface area of 1.2 m ² / g were mixed and stored at room temperature for 10 days. There was no particular change in the appearance after storage. This mixture was calcined in air at 950 ° C. for 12 hours. The composition of the obtained composite oxide was LiAl _0.01 Co _0.975 Mg _0.01 Zr _0.005 O ₂ .

The particle size distribution of the substantially spherical lithium-containing composite oxide powder formed by aggregation of the obtained primary particles was measured using a laser scattering particle size distribution measuring device. As a result, the average particle diameter D50 was 16.3 μm, D10 was 6.0 μm, D90 was 23.3 μm, and the specific surface area determined by the BET method was 0.33 m ² / g. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.107 °. The press density of the powder was 3.21 g / cm ³ . Further, 10 g of the above powder was dispersed in 100 g of pure water, filtered and subjected to potentiometric titration with 0.1N HCl to determine the residual alkali amount, which was 0.02% by mass.

  Using the above lithium-containing composite oxide powder, a positive electrode body was produced in the same manner as in Example 1-1, a battery was assembled, and its characteristics were measured. The initial weight capacity density of the positive electrode layer was 161 mAh / g, and the capacity retention after 30 charge / discharge cycles was 99.5%. The heat generation start temperature of the 4.3V charged product was 175 ° C.

[Example 1-3]
In addition to the same mixture used in Example 1-1, a complex solution containing an additive element in which 30 g of ethanol was added to a mixture of 193.18 g of cobalt hydroxide powder and 76.56 g of lithium carbonate powder was mixed. Was dried in the same manner as in Example 1-1 and stored at room temperature for 10 days. The appearance after storage changed from greenish brown to brown. This mixture was calcined in air at 950 ° C. for 12 hours. The composition of the obtained composite oxide was LiAl _0.01 Co _0.979 Mg _0.01 Ti _0.001 O ₂ .

The particle size distribution of the obtained bulk lithium-containing composite oxide powder was measured using a laser scattering type particle size distribution measuring device. As a result, the average particle diameter D50 was 12.1 μm, D10 was 4.3 μm, D90 was 19.4 μm, and the specific surface area determined by the BET method was 0.48 m ² / g. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.117 °. The press density of the powder was 3.06 g / cm ³ .

  Further, 10 g of the above powder was dispersed in 100 g of pure water, filtered and subjected to potentiometric titration with 0.1N HCl to determine the residual alkali amount, which was 0.02% by mass. In the same manner as in Example 1-1, a positive electrode body was manufactured, a battery was assembled, and its characteristics were measured. The initial weight capacity density of the positive electrode layer was 157 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 98.1%. The heat generation start temperature of the 4.3V charged product was 169 ° C.

[Example 1-4]
In addition to the same mixture used in Example 1-1, a mixture solution containing 191.99 g of cobalt hydroxide powder and 76.40 g of lithium carbonate powder was mixed with a complex solution containing additional elements added with 30 g of ethanol. Was dried in the same manner as in Example 1-2 and then stored at room temperature for 10 days. The appearance after storage changed from greenish brown to brown. This mixture was calcined in air at 950 ° C. for 12 hours. The composition of the obtained composite oxide was LiAl _0.01 Co _0.975 Mg _0.01 Zr _0.005 O ₂ .

The particle size distribution of the obtained bulk lithium-containing composite oxide powder was measured using a laser scattering type particle size distribution measuring device. As a result, the average particle diameter D50 was 12.5 μm, D10 was 3.6 μm, D90 was 18.5 μm, and the specific surface area determined by the BET method was 0.51 m ² / g. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane around 2θ = 66.5 ± 1 ° was 0.125 °. The press density of the powder was 3.00 g / cm ³ .

Moreover, it carried out similarly to Example 1-1, manufactured the positive electrode body, assembled the battery, and measured the characteristic. The initial weight capacity density of the positive electrode layer was 159 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 97.9%. The heat generation start temperature of the 4.3V charged product was 169 ° C.
[Example 2-1]
According to a known method, a cobalt hydroxide aqueous solution and ammonium hydroxide mixed solution and a caustic soda aqueous solution were continuously mixed to continuously prepare a cobalt hydroxide slurry. Next, the slurry was subjected to agglomeration, filtration, and drying steps to obtain cobalt hydroxide powder. The obtained cobalt hydroxide has a diffraction peak half-width of (001) plane of 2θ = 19 ± 1 ° in powder X-ray diffraction using CuKα ray is 0.27 °, and 2θ = 38 ° ± 1. The diffraction peak half-value width of the (101) plane was 0.23 °, and as a result of observation with a scanning electron microscope, it was found that the fine particles were aggregated and formed from substantially spherical secondary particles. As a result of volume-based particle size distribution analysis obtained from image analysis under scanning electron microscope observation, the average particle size D50 was 17.5 μm, D10 was 7.1 μm, and D90 was 26.4 μm. The cobalt content of cobalt hydroxide was 61.5% by mass.
190.61 g of the cobalt hydroxide powder was mixed with 76.24 g of lithium carbonate powder having a specific surface area of 1.2 m ² / g.

  On the other hand, 1.74 g of diethylene glycol and 2.46 g of triethylene glycol were added to 5.26 g of magnesium nitrate hexahydrate and stirred until it was completely dissolved. After complete dissolution, 44.87 g of ethanol was added and further stirred. To the resulting solution was added 10.02 g of a mixed solution of titanium acetylacetonate in xylene / 1-butanol (1: 1) (Ti content: 9.8 mass%), and aluminum ethyl acetoacetate diisopropylate was added in an amount of 5. An additive element solution was obtained by adding 65 g and stirring.

The additive element solution was mixed with the mixture of the cobalt hydroxide powder and the lithium carbonate powder so as to form a slurry. In this case, the mixing ratio of cobalt hydroxide, lithium carbonate, magnesium nitrate hexahydrate, aluminum ethyl acetoacetate diisopropylate, titanium acetylacetonate was LiAl _0.01 Co _0.97 Mg _0.01 Ti _{0. 0} after firing _. It was formulated as a ₀₁ O _2.

The slurry was desolvated with a rotary evaporator and then calcined in air at 950 ° C. for 12 hours. As a result of measuring the particle size distribution of the lithium-containing composite oxide powder obtained by agglomerating primary particles obtained by crushing the fired product in a water solvent using a laser scattering type particle size distribution measuring device, the average particle size D50 Was 13.0 μm, D10 was 7.0 μm, D90 was 18.0 μm, and a substantially spherical lithium-containing composite oxide powder having a specific surface area of 0.38 m ² / g determined by the BET method was obtained. With respect to this lithium-containing composite oxide powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.110 °. The press density of this powder was 3.21 g / cm ³ . 10 g of this lithium-containing composite oxide powder was dispersed in 100 g of pure water, filtered, and potentiometrically titrated with 0.1 N HCl to determine the residual alkali amount, which was 0.02% by mass.

  The lithium-containing composite oxide powder, acetylene black, and polyvinylidene fluoride powder are mixed at a mass ratio of 90/5/5, N-methylpyrrolidone is added to prepare a slurry, and aluminum having a thickness of 20 μm is prepared. The foil was coated on one side using a doctor blade. The positive electrode sheet for lithium batteries was produced by drying and performing roll press rolling 5 times.

The positive electrode sheet is used for the positive electrode, a metal lithium foil having a thickness of 500 μm is used for the negative electrode, a nickel foil of 20 μm is used for the negative electrode current collector, and a porous polypropylene having a thickness of 25 μm is used for the separator. Further, the electrolytic solution is a LiPF ₆ / EC + DEC (1: 1) solution having a concentration of 1 M (meaning a mixed solution of EC and DEC in a mass ratio (1: 1) containing LiPF ₆ as a solute. Solvents described later are also this). The two stainless steel simple sealed cell type lithium batteries were assembled in an argon glove box.

  For the one battery, the initial discharge capacity was charged at 25 ° C. with a load current of 75 mA per gram of the positive electrode active material to 4.3 V and discharged with a load current of 75 mA per gram of the positive electrode active material to 2.5 V. Asked. Furthermore, the density of the electrode layer was determined. Moreover, about this battery, the charging / discharging cycle test was done 30 times continuously. As a result, the initial weight capacity density of the positive electrode layer at 25 ° C. and 2.5 to 4.3 V was 162 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.2%.

  The other battery was charged at 4.3 V for 10 hours, disassembled in an argon glove box, and the charged positive electrode sheet was taken out. The positive electrode sheet was washed, punched out to a diameter of 3 mm, sealed in an aluminum capsule together with EC, and heated at a rate of 5 ° C./min with a scanning differential calorimeter to measure the heat generation start temperature. As a result, the heat generation start temperature of the 4.3V charged product was 176 ° C.

[Example 2-2]
Example 2-1 was carried out in the same manner as Example 2-1 except that the following solution was used as the additive element solution. That is, 1.74 g of diethylene glycol and 2.46 g of triethylene glycol were added to 5.26 g of magnesium nitrate hexahydrate, and the mixture was stirred until completely dissolved. After completely dissolved, 36.45 g of ethanol was added and stirred. To this solution was added 18.44 g of a mixed solution of zirconium tributoxide monoacetylacetonate in xylene / 1-butanol (1: 1) (ZrO ₂ content: 13.8 mass%), and aluminum ethyl acetoacetate diisopropylate was further added. A solution of the additive element was prepared by adding 5.65 g and stirring.

In this way, a positive electrode active material having LiAl _0.01 Co _0.97 Mg _0.01 Zr _0.01 O ₂ was synthesized in the fired product. As a result of measuring the particle size distribution of the lithium-containing composite oxide powder obtained by agglomerating primary particles obtained by crushing the fired product using a laser scattering type particle size distribution measuring device, the average particle size D50 is 15.9 μm, A substantially spherical powder having a D10 of 4.1 μm, a D90 of 23.8 μm and a specific surface area of 0.40 m ² / g determined by the BET method was obtained. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.111 °. The press density of the powder was 3.19 g / cm ³ . Further, 10 g of the above powder was dispersed in 100 g of pure water, filtered and subjected to potentiometric titration with 0.1N HCl to determine the residual alkali amount, which was 0.02% by mass.

  Using the above lithium-containing composite oxide powder, a positive electrode body was produced in the same manner as in Example 2-1, a battery was assembled, and its characteristics were measured. The initial weight capacity density of the positive electrode layer was 160 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.5%. The heat generation start temperature of the 4.3V charged product was 175 ° C.

[Example 2-3] Comparative Example A lithium-containing oxide that becomes LiCoO ₂ after firing was synthesized in the same manner as in Example 2-1, except that the additive element solution was not added. An agglomerated LiCoO ₂ powder having an average particle diameter D50 of 14.0 μm, D10 of 11.2 μm, D90 of 17.3 μm and a specific surface area determined by the BET method of 0.25 m ² / g was obtained. With respect to the LiCoO ₂ powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.108 °. The press density of the obtained LiCoO ₂ powder was 3.22 g / cm ³ .
In the same manner as in Example 2-1, a positive electrode body was manufactured, a battery was assembled, and its characteristics were measured. The initial weight capacity density of the positive electrode layer was 160 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 96.9%. The heat generation start temperature of the 4.3V charged product was 157 ° C.

[Example 2-4] Comparative Example In Example 2-1, instead of the additive element solution, 1.97 g of solid magnesium hydroxide (Mg content: 25.26 mass%) and 1.60 g of aluminum hydroxide were used. A positive electrode active material which is LiAl _0.01 Co _0.97 Mg _0.01 Ti _0.01 O ₂ after firing in the same manner as in Example 2-1, except that 1.64 g of titanium oxide was used and mixed in a solid phase. Was synthesized. The press density of this powder was 2.99 g / cm ³ .
Moreover, it carried out similarly to Example 2-1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 161 mAh / g, the capacity retention after 30 cycles was 97.8%, and the heat generation starting temperature was 161 ° C.

[Example 2-5] (Comparative Example)
In Example 2-2, instead of the additive element solution, 1.97 g of solid magnesium hydroxide, 1.60 g of aluminum hydroxide and 1.87 g of zirconium oxide were used and mixed in the solid phase, except for Example 2- In the same manner as in Example ₂ , a positive electrode active material that was LiAl _0.01 Co _0.97 Mg _0.01 Zr _0.01 O ₂ was synthesized after firing.
The press density of this powder was 2.95 g / cm ³ . Further, 10 g of this powder was dispersed in 100 g of pure water, filtered and subjected to potentiometric titration with 0.1N HCl to obtain the residual alkali amount, which was 0.02% by mass.
In the same manner as in Example 2-1, a positive electrode body was manufactured, a battery was assembled, and its characteristics were measured. The initial weight capacity density of the positive electrode layer was 161 mAh / g, the capacity retention rate after 30 cycles was 97.9%, and the heat generation starting temperature was 163 ° C.

[Example 2-6]
In Example 2-2, a positive electrode active material was synthesized in the same manner as in Example 2-1, except that lithium fluoride powder was further added to mix cobalt hydroxide and lithium carbonate. The additive element solution used in Example 2-2 was mixed with a mixture of 190.61 g of cobalt hydroxide, 75.86 g of lithium carbonate, and 0.27 g of lithium fluoride so as to form a slurry. After firing, a positive electrode active material that was LiAl _0.01 Co _0.97 Mg _0.01 Zr _0.01 O _1.995 F _0.005 was synthesized.
The press density of this powder was 3.19 g / cm ³ .
Moreover, it carried out similarly to Example 2-1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 161 mAh / g, the capacity retention ratio after 30 cycles was 99.7%, and the heat generation start temperature was 175 ° C.

[Example 2-7] (Comparative Example)
In Example 2-6, instead of the additive element solution, solid magnesium hydroxide, aluminum hydroxide, and zirconium oxide were used, and the mixture was mixed in a solid phase, and then calcined and LiAl _0.01 Co. _A positive electrode active material of _0.97 Mg _0.01 Zr _0.01 O _1.995 F _0.005 was synthesized.
The press density of this powder was 3.08 g / cm ³ .
Moreover, it carried out similarly to Example 2-1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 160 mAh / g, the capacity retention rate after 30 cycles was 98.3%, and the heat generation start temperature was 168 ° C.

[Example 3-1]
Cobalt hydroxide powder and ammonium hydroxide mixed solution and caustic soda aqueous solution are continuously mixed to synthesize a cobalt hydroxide slurry continuously by a known method, and then go through agglomeration, filtration and drying steps to obtain cobalt hydroxide powder. Got. The obtained cobalt hydroxide has a diffraction peak half-width of (001) plane of 2θ = 19 ± 1 ° in powder X-ray diffraction using CuKα ray is 0.27 °, and 2θ = 38 ° ± 1. The diffraction peak half-value width of the (101) plane was 0.23 °, and as a result of observation with a scanning electron microscope, it was found that the fine particles were aggregated and formed from substantially spherical secondary particles. As a result of volume-based particle size distribution analysis obtained from image analysis under scanning electron microscope observation, the average particle size D50 was 13.2 μm, D10 was 9.1 μm, and D90 was 17.0 μm. The cobalt content of cobalt hydroxide was 61.5%.

191.46 g of the above cobalt hydroxide powder and 76.58 g of lithium carbonate powder having a specific surface area of 1.2 m ² / g were mixed and then calcined in air at 950 ° C. for 12 hours to synthesize lithium cobalt oxide powder. .

  On the other hand, 1.74 g of diethylene glycol and 2.46 g of triethylene glycol were added to 5.26 g of magnesium nitrate hexahydrate and stirred until it was completely dissolved. After complete dissolution, 54.87 g of ethanol was added and further stirred. To this solution was added 10.02 g of a mixed solution of titanium acetylacetonate in xylene / 1-butanol (1: 1) (Ti content: 9.8 mass%), and 5.65 g of aluminum ethyl acetoacetate diisopropylate. By adding and stirring, a complex solution containing the additive element was obtained.

The lithium cobaltate powder was mixed with a complex solution containing the additive element so as to form a slurry. The mixing ratio of magnesium nitrate hexahydrate, aluminum ethyl acetoacetate diisopropylate and titanium acetylacetonate is such that the composition after firing is LiAl _0.01 Co _0.97 Mg _0.01 Ti _0.01 O ₂ Blended.

The slurry was desolvated with a rotary evaporator and then calcined in air at 900 ° C. for 12 hours. As a result of measuring the particle size distribution of the lithium-containing composite oxide powder obtained by crushing the fired product and aggregating the obtained primary particles in a water solvent using a laser scattering type particle size distribution analyzer, the average particle size D50 is 13.1 μm, D10 is 9.2 μm, D90 is 16.9 μm, and a substantially spherical lithium-containing composite oxide powder LiAl _0.01 Co ₀ having a specific surface area of 0.37 m ² / g determined by the BET method. _.97 Mg _0.01 Ti _0.01 O ₂ was obtained.

With respect to this lithium-containing composite oxide powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.112 °. The press density of this powder was 3.03 g / cm ³ . 10 g of this lithium-containing composite oxide powder was dispersed in 100 g of pure water, filtered, and potentiometrically titrated with 0.1 N HCl to determine the residual alkali amount, which was 0.02% by mass.

  The lithium-containing composite oxide powder, acetylene black, and polyvinylidene fluoride powder are mixed at a mass ratio of 90/5/5, N-methylpyrrolidone is added to prepare a slurry, and aluminum having a thickness of 20 μm is prepared. The foil was coated on one side using a doctor blade. The positive electrode sheet for lithium batteries was produced by drying and performing roll press rolling 5 times.

The positive electrode sheet is punched out as a positive electrode, a metal lithium foil having a thickness of 500 μm is used as a negative electrode, a nickel foil of 20 μm is used as a negative electrode current collector, and a porous polypropylene having a thickness of 25 μm is used as a separator. Further, the electrolytic solution used is a LiPF ₆ / EC + DEC (1: 1) solution having a concentration of 1 M (meaning a mixed solution of EC and DEC having a mass ratio (1: 1) of LiPF ₆ as a solute. Solvents described later) In accordance with this, two stainless steel simple sealed cell type lithium batteries were assembled in an argon glove box.

  For the one battery, the initial discharge capacity was charged at 25 ° C. with a load current of 75 mA per gram of the positive electrode active material to 4.3 V and discharged with a load current of 75 mA per gram of the positive electrode active material to 2.5 V. Asked. Furthermore, the density of the electrode layer was determined. Moreover, about this battery, the charging / discharging cycle test was done 30 times continuously. As a result, the initial weight capacity density of the positive electrode layer at 25 ° C. and 2.5 to 4.3 V was 160 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 99.7%.

  The other battery was charged at 4.3 V for 10 hours, disassembled in an argon glove box, taken out of the positive electrode sheet after charging, washed the positive electrode sheet, punched into a diameter of 3 mm, and together with EC The container was sealed in an aluminum capsule and heated at a rate of 5 ° C./min with a scanning differential calorimeter to measure the heat generation start temperature. As a result, the heat generation start temperature of the 4.3V charged product was 177 ° C.

[Example 3-2]
After mixing 190.61 g of the cobalt hydroxide powder of Example 3-1 and 76.24 g of lithium carbonate powder having a specific surface area of 1.2 m ² / g, the mixture was calcined in the air at 950 ° C. for 12 hours to form a lithium cobalt composite. Oxide powder was synthesized.

On the other hand, 1.74 g of diethylene glycol and 2.46 g of triethylene glycol were added to 5.26 g of magnesium nitrate hexahydrate and stirred until it was completely dissolved. After complete dissolution, 46.45 g of ethanol was added and stirred. To this solution was added 18.44 g of a mixed solution of zirconium tributoxide acetylacetonate in xylene / 1-butanol (1: 1) (ZrO ₂ content: 13.8% by mass), and then aluminum ethyl acetoacetate diisopropylate. Was added and stirred to obtain a complex solution containing the additive element.

Except having used said lithium containing complex oxide powder and additive element liquid, it carried out similarly to Example 3-1. The resulting fired product was crushed, and the particle size distribution of the lithium-containing composite oxide powder obtained by agglomerating the primary particles was measured in a water solvent using a laser scattering particle size distribution analyzer. As a result, the average particle diameter D50 was 13.5 μm, D10 was 9.9 μm, and D90 was 17.2 μm. The specific surface area determined by the BET method was 0.35 m ² / g, and the powder was a substantially spherical powder having a composition of LiAl _0.01 Co _0.97 Mg _0.01 Zr _0.01 O ₂ .

With respect to this lithium-containing composite oxide powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane at 2θ = 66.5 ± 1 ° was 0.120 °. The press density of this powder was 3.00 g / cm ³ . 10 g of this lithium-containing composite oxide powder was dispersed in 100 g of pure water, filtered, and potentiometrically titrated with 0.1 N HCl to determine the residual alkali amount, which was 0.02% by mass.

  Using the above lithium-containing composite oxide powder, a positive electrode body was produced in the same manner as in Example 3-1, a battery was assembled, and its characteristics were measured. As a result, the initial weight capacity density of the positive electrode layer was 163 mAh / g, and the capacity retention after 30 charge / discharge cycles was 99.5%. Moreover, the heat generation start temperature of the 4.3V charged product was 177 ° C.

[Example 3-3] Comparative Example In Example 3-1, a complex solution containing an additive element was not used. Instead, 1.20 g of magnesium hydroxide, 1.60 g of aluminum hydroxide, and 1.1 of titanium oxide were used. The same procedure as in Example 3-1 was performed except that 65 g of the mixed powder was used and the composition after firing was LiAl _0.01 Co _0.97 Mg _0.01 Ti _0.01 O ₂ . This powder was calcined in air at 950 ° C. for 12 hours.

As a result of measuring the particle size distribution of the obtained powder in an aqueous solvent using a laser scattering particle size distribution measuring device, the average particle size D50 was 13.1 μm, D10 was 9.0 μm, and D90 was 16.8 μm. . The specific surface area determined by the BET method was 0.35 m ² / g. Similarly, in the powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane near 2θ = 66.5 ± 1 ° was 0.131 °. The press density of this powder was 2.91 g / cm ³ .

  Moreover, it carried out similarly to Example 3-1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 159 mAh / g, the capacity retention after 30 cycles was 98.2%, and the heat generation starting temperature was 156 ° C.

[Example 3-4] (Comparative Example)
In Example 3-2, the complex solution containing the additive element was not used, and instead, a mixed powder of 1.60 g of magnesium hydroxide, 1.60 g of aluminum hydroxide, and 2.53 g of zirconium oxide was used. and except that the composition after firing was blended so that _{LiAl 0.01 Co 0.97 Mg 0.01 Zr 0.01} O 2 was carried out in the same manner as example 3-1. This powder was calcined in air at 950 ° C. for 12 hours.

As a result of measuring the particle size distribution of the obtained powder in an aqueous solvent using a laser scattering particle size distribution measuring apparatus, the average particle size D50 was 13.3 μm, D10 was 9.3 μm, and D90 was 17.1 μm. . The specific surface area determined by the BET method was 0.33 m ² / g. Similarly, in powder X-ray diffraction using CuKα rays, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.128 °. The press density of this powder was 2.88 g / cm ³ .
Moreover, it carried out similarly to Example 3-1, the positive electrode body was manufactured, the battery was assembled, and the characteristic was measured. The initial weight capacity density of the positive electrode layer was 160 mAh / g, the capacity retention after 30 cycles was 98.5%, and the heat generation starting temperature was 160 ° C.

[Example 4-1]
Instead of the cobalt hydroxide powder, a commercially available cobalt oxyhydroxide having an average particle size of 13.5 μm was used as a cobalt source. As a result of observation with a scanning electron microscope, cobalt oxyhydroxide was found to be formed of substantially spherical secondary particles by agglomeration of fine particles. As a result of volume-based particle size distribution analysis obtained from image analysis under scanning electron microscope observation, the average particle size D50 was 13.5 μm, D10 was 6.6 μm, and D90 was 18.2 μm. The cobalt content of the cobalt oxyhydroxide was 62.0% by mass.

  On the other hand, 0.44 g of diethylene glycol and 0.62 g of triethylene glycol were added to 1.32 g of magnesium nitrate hexahydrate and stirred until it was completely dissolved. Further, 0.41 g of acetylacetone is added to 0.65 g of niobium (V) ethoxide, refluxed at 70 ° C. for 30 minutes and cooled to room temperature, then added with 0.84 g of ethanol and stirred for 10 minutes to give a 10 mass% niobium solution. Got. A complex solution containing an additive element by mixing 4.27 g of aluminum ethyl acetoacetate diisopropylate and 41.45 g of ethanol in a stirred solution after mixing a glycol / ethanol solution of magnesium nitrate with a 10 mass% niobium solution. Got.

192.69 g of the cobalt oxyhydroxide and the additive element solution were mixed so as to form a slurry. The mixture was desolvated with a rotary evaporator and then mixed with 76.08 g of lithium carbonate having a specific surface area of 1.2 m ² / g. This mixture was baked at 990 ° C. for 12 hours in an oxygen-containing atmosphere to obtain a lithium-containing composite oxide having a LiAl _0.0075 Co _0.989 Mg _0.0025 Nb _0.001 O ₂ composition. An agglomerated lithium-containing composite oxide powder having an average particle diameter D50 of 15.5 μm, D10 of 7.3 μm, D90 of 19.6 μm and a specific surface area of 0.30 m ² / g determined by the BET method was obtained. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane around 2θ = 66.5 ± 1 ° was 0.101 °. The press density of the obtained lithium-containing composite oxide powder was 3.15 g / cm ³ . Moreover, pH was 10.8 and the alkali amount by titration was 0.02 mass%.
Moreover, it carried out similarly to Example 1-1, manufactured the positive electrode body, assembled the battery, and measured the characteristic. The initial weight capacity density of the positive electrode layer was 156 mAh / g, the capacity retention after 30 cycles was 98.3%, and the heat generation starting temperature was 172 ° C.

[Example 4-2]
To 5.28 g of magnesium nitrate hexahydrate, 1.75 g of diethylene glycol and 2.47 g of triethylene glycol were added and stirred until completely dissolved. To this solution, 5.66 g of aluminum ethyl acetoacetate diisopropylate and 34.84 g of ethanol were added and stirred to obtain a complex solution containing additional elements. The obtained complex solution containing the additive element was mixed with 194.54 g of Ni _0.8 Co _0.2 (OH) ₂ powder having a metal content of 61.0% by mass and dried in the same manner as in Example 4-1. Processed. The mixture obtained was mixed with 49.68 g of lithium hydroxide having a lithium content of 28.8% by mass, baked at 500 ° C. for 12 hours in an oxygen-containing atmosphere, mixed in a mortar, and then mixed in an oxygen-containing atmosphere. And baked at 760 ° C. for 12 hours.

The composition of the obtained lithium-containing composite oxide was LiNi _0.784 Co _0.196 Al _0.01 Mg _0.01 O ₂ . An agglomerated lithium-containing composite oxide powder having an average particle diameter D50 of 13.6 μm, D10 of 5.8 μm, D90 of 17.1 μm, and a specific surface area determined by the BET method of 0.35 m ² / g was obtained. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). CuKα radiation was used. In powder X-ray diffraction, the half value width of the diffraction peak of (110) plane around 2θ = 66.5 ± 1 ° was 0.131 °. The press density of the obtained lithium-containing composite oxide powder was 3.00 g / cm ³ . Moreover, pH was 11.8 and the alkali amount by titration was 3.10 mass%.
Moreover, it carried out similarly to Example 1-1, manufactured the positive electrode body, assembled the battery, and measured the characteristic. The initial weight capacity density of the positive electrode layer was 188 mAh / g, the capacity retention after 30 cycles was 98.7%, and the heat generation starting temperature was 161 ° C.

[Example 4-3]
By mixing and stirring 1.90 g of a mixed solution of zirconium tributoxide monoacetylacetonate in xylene / 1-butanol (1: 1) (ZrO ₂ : 13.8% by mass) and 48.10 g of ethanol, the added elements were mixed. A complex solution containing was obtained. The obtained complex solution containing the additive element was mixed with 193.64 g of Ni _1/3 Co _1/3 Mn _1/3 OOH powder having a metal content of 60.0% by mass, followed by drying treatment in the same manner as in Example 4-1. Went. The obtained mixture was mixed with 82.95 g of lithium carbonate having a lithium content of 18.7% by mass and calcined at 1000 ° C. for 12 hours in an oxygen-containing atmosphere.

The composition of the obtained lithium-containing composite oxide was Li _1.05 (Ni _1/3 Co _1/3 Mn _1/3 ) _0.949 Zr _0.001 O ₂ . A bulky lithium-containing composite oxide powder having an average particle diameter D50 of 12.6 μm, D10 of 6.2 μm, D90 of 17.5 μm and a specific surface area of 0.38 m ² / g determined by the BET method was obtained. With respect to this powder, an X-ray diffraction spectrum was obtained using an X-ray diffractometer (RINT 2100 type, manufactured by Rigaku Corporation). In powder X-ray diffraction using CuKα ray, the half value width of the diffraction peak of (110) plane in the vicinity of 2θ = 66.5 ± 1 ° was 0.190 °. The press density of the obtained lithium-containing composite oxide powder was 3.10 g / cm ³ . Moreover, pH was 11.0 and the alkali amount by titration was 0.33 weight%.
Moreover, it carried out similarly to Example 1-1, manufactured the positive electrode body, assembled the battery, and measured the characteristic. The initial weight capacity density of the positive electrode layer was 159 mAh / g, the capacity retention after 30 cycles was 97.2%, and the heat generation start temperature was 197 ° C.

  According to the present invention, a method for producing a lithium-containing composite oxide for a lithium secondary battery positive electrode having a large volumetric capacity density, high safety, excellent charge / discharge cycle durability and low temperature characteristics, and high productivity The positive electrode for lithium secondary batteries containing the manufactured lithium containing complex oxide, and a lithium secondary battery are provided.

Claims (14)

Formula _{Li p N x M m O z} F a ( where, N is the Co, at least one element selected from the group consisting of Mn and Ni, M is a transition metal element other than N, Al and alkaline earth It is at least one element selected from the group consisting of metal elements: 0.9 ≦ p ≦ 1.2, 0.9 ≦ x <1.00, 0 <m ≦ 0.03, 1.9 ≦ z ≦ 2.2, x + m = 1, 0 ≦ a ≦ 0.02), wherein the complex containing M element is dissolved in an organic solvent as the M element source. The manufacturing method of the lithium containing complex oxide for lithium secondary battery positive electrodes characterized by using the solution which is used.   The complex containing the M element is a chelate complex of the M element, a glycol complex of the nitrate or chloride of the M element, or a β-diketone complex of the nitrate or chloride of the M element, and the organic solvent is a polar organic solvent. 2. The production method according to 1.   2. The production method according to claim 1, wherein the complex containing M element is a complex containing a β-diketone group of M element and an alkoxide group, or a complex of diethylene glycol and triethylene glycol of nitrate of M element.   The production method according to any one of claims 1 to 3, wherein the M element is at least one selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Mg, Cu, Sn, Zn, and Al.   5. The element according to claim 1, wherein the M element comprises at least Al and Mg, Al / Mg is 1/5 to 5/1 in atomic ratio, and 0.002 ≦ m ≦ 0.025. Production method.   M element consists of Mg and M2 (M2 is at least one element selected from the group consisting of at least Ti, Zr, Ta, and Nb), and M2 / Mg is 1/40 to 2/1 in atomic ratio, And it is 0.002 <= m <= 0.025, The manufacturing method in any one of Claims 1-4. A solution in which a complex containing M element is dissolved in an organic solvent, an N source compound powder, and, if necessary, a fluorine source compound powder are mixed, and after removing the organic solvent from the resulting mixture, a lithium source compound powder, And the fluorine source compound powder is mixed as needed, and then it is manufactured by firing at 800 to 1050 ° C. in an oxygen-containing atmosphere.   A solution in which a complex containing M element is dissolved in an organic solvent, an N source compound powder, a lithium source compound powder, and, if necessary, a fluorine source compound powder are mixed, and after removing the organic solvent from the resulting mixture, The production method according to any one of claims 1 to 6, wherein the firing is performed at 800 to 1050C in an oxygen-containing atmosphere.   Lithium source compound powder, N source compound powder, and, if necessary, a solution containing a lithium source compound powder and a lithium-containing composite oxide powder obtained by firing and a complex containing M element dissolved in an organic solvent And the organic solvent is removed from the resulting mixture, followed by firing at 300 to 1050 ° C. in an oxygen-containing atmosphere. The integrated width of the diffraction peak of the (110) plane of 2θ = 66 to 67 ° measured by X-ray diffraction using CuKα as the radiation source of the lithium-containing composite oxide is 0.08 to 0.14, and the surface area is 0. .2~0.6m ² / g, the process according to any one of claims 1 to 9 heat generation starting temperature of 160 ° C. or higher. The manufacturing method according to any one of claims 1 to 10, wherein the lithium-containing composite oxide has a filling press density of 3.15 to 3.60 g / cm ³ . The manufacturing method according to any one of claims 1 to 11, wherein the amount of residual alkali contained in the lithium-containing composite oxide is 0.03% by mass or less.   The positive electrode for lithium secondary batteries containing the lithium containing complex oxide manufactured by the manufacturing method in any one of Claims 1-12.   A lithium secondary battery using the positive electrode according to claim 13.